1. Technical Field
The present inventive concept relates to a universal serial bus (USB) device and a USB system including the same.
2. Discussion of the Related Art
Universal serial bus (USB) is an industry standard that defines the cables, connectors and communications protocols used in a bus for connection, communication and power supply between computers and electronic devices, for example.
A USB device may operate in various modes and provide a different function in each mode. The USB device requires a different combination of function drivers in each mode. Therefore, when the mode of the USB device is changed, function drivers needed for the changed mode should be loaded to a volatile memory of the USB device.
Function drivers may be loaded from a nonvolatile memory to the volatile memory. Combinations of function drivers required for each mode may be stored in the nonvolatile memory. For example, a first combination may be a combination of function drivers needed to operate the USB device in a first mode, and a second combination may be a combination of function drivers needed to operate the USB device in a second mode. Therefore, when the mode of the USB device is changed, all function drivers loaded in the volatile memory may be unloaded. Then, function drivers included in a combination of function drivers needed for the changed mode may be loaded from the nonvolatile memory to the volatile memory.
However, some of the function drivers present in the volatile memory before a mode change of the USB device may be required by the new mode. Therefore, the unloading of all the function drivers from the volatile memory may be inefficient.